Sheet metal pulley

ABSTRACT

A sheet metal pulley has a base part and a cylindrical peripheral wall for winding a belt formed integrally with the base part. An ear is disposed in an end part of the cylindrical peripheral wall. The base part is partitioned into an inner peripheral portion and an outer peripheral portion, with the inner peripheral portion being smoothly connected with the outer peripheral portion through a bent part. The outer peripheral portion is formed into a tapered shape which extends from the bent part and has a diameter which is increased toward the inner side of the cylindrical peripheral wall in the axial direction of the pulley. The outer peripheral portion connected with an end part of the peripheral wall on the side of the ear. Even when the pulley is used for a long term, the connecting portion between the peripheral wall and the base part, etc. is hardly cracked.

TECHNICAL FIELD

The present invention relates to a sheet metal pulley, and particularlyto a sheet metal pulley having an annular ear which projects outwardfrom an end part of a cylindrical peripheral wall for winding a belt.

BACKGROUND ART

FIGS. 3 and 5 show a prior art sheet metal pulley A in which a circularbase part and a peripheral wall for winding a belt are integrally formedby working, or the like, a flat sheet metal blank.

The sheet metal pulley A of FIG. 3 has a recess part 11 foraccommodating a bearing (not shown), in an inner peripheral portion of acircular base part 1. A cylindrical peripheral wall 2 having poly-Vgrooves 21 and an ear 22 is integrally formed in the outer peripheralend of the base part 1. The base part 1 has a flat annular part 12surrounding the recess part 11. The ear 22 has a double layer structureconsisting of a first inclined part 23 which extends from the annularpart 12 on the side of the base part 1, and a second inclined part 24which is folded toward one face of the first inclined part 23 so as tooverlap with the first inclined part.

In the sheet metal pulley A of FIG. 5, an ear 22 is formed so as to havea single layer structure, and the end part of the peripheral wall 2 onthe side of the ear 22 is integrally connected with the base part 1.

In the sheet metal pulley A of FIG. 3, when a poly-V belt (not shown) iswound around the peripheral wall 2 and the pulley A is then operated, acrack a which is directed from the inner side to the outer side may beformed in a relatively short period in a folded portion 25 in thevicinity of the boundary of the first inclined part 23 and the secondinclined part 24 as shown in FIG. 4. Also in the sheet metal pulley A ofFIG. 5, a crack a which is directed from the inner side to the outerside may be formed in a relatively short period in a connecting portion26 between the end part of the peripheral wall 2 on the side of the ear22 and the base part 1.

The formation of the crack a and its cause in the sheet metal pulley Ahas intensively been investigated. As a result, it is found that, whenthe pulley is operated, the peripheral wall 2 around which a belt iswound, vibrates or oscillates about the folded portion 25 or theconnecting portion 26 functioning as the fulcrum, with the result thatthe folded portion 25 or the connecting portion 26 is excessivelyfatigued.

The present invention is a result of studying the above-mentionedcircumstances. It is, therefore, an object of the present invention toprovide a sheet metal pulley in which a crack is hardly formed, byimproving the structure of a base part connected with an end part of aperipheral wall so that, even when the peripheral wall vibrates oroscillates as the pulley is operated, fatigue is prevented fromexcessively occurring in one position.

SUMMARY OF THE INVENTION

In order to attain the noted object, a sheet metal pulley according tothe present invention has a base part and a cylindrical peripheral wallfor winding a belt integrally formed with it and has an annular earprojecting outward from an end part of the peripheral wall. The pulleyis configured so that the base part is partitioned into an innerperipheral portion and an outer peripheral portion, the inner peripheralportion being connected with the outer peripheral portion through a bentpart, and the outer peripheral portion being formed into a tapered shapewhich extends from the bent part. The diameter of the outer peripheralportion is increased toward the inner side in the axial direction of thepulley, and is connected with the end part of the peripheral wall on theside of the ear.

In another embodiment of a sheet metal pulley according to the presentinvention, in addition to the above-mentioned configuration, a recesspart into which a bearing is to be fitted is disposed in the innerperipheral portion of the base part.

In the sheet metal pulley described above, when a belt is wound aroundthe pulley and the pulley is operated (at high rpm), vibration andoscillation of the peripheral wall are sufficiently propagated to theouter peripheral portion so that vibration and oscillation effectivelyoccur also in the outer peripheral portion. In this case, the fulcrumsof the vibration and oscillation are scattered in the end part of theperipheral wall on the side of the ear and also in the bent part, andhence the bending fatigue due to the vibration and oscillation is notconcentrated into the end part of the peripheral wall. Therefore,cracking in the end part of the peripheral wall on the side of the earis prevented for a long term.

In order to effectively prevent the crack formation from occurring, thetaper angle of the outer peripheral portion may be set to be in therange of 15° to 70° or preferably 25 to 50 with respect to a horizontalaxis perpendicularly intersecting with the axial direction of thepulley.

In the case where a recess part is disposed in the inner peripheralportion of the base part, a bearing is fitted into the recess part to beattached to the pulley.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical section view of a sheet metal pulley according to afirst embodiment of the present invention.

FIG. 2 is a vertical section view of a sheet metal pulley according to asecond embodiment of the present invention.

FIG. 3 is a vertical section view of a prior art sheet metal pulley.

FIG. 4 is an enlarged section view of the section IV of FIG. 3.

FIG. 5 is a vertical section view of another prior art sheet metalpulley.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In a sheet metal pulley A according to a first embodiment of the presentinvention and shown in FIG. 1, a base part 1 is partitioned into aninner peripheral portion 13 and an outer peripheral portion 14. Theinner peripheral portion 13 is smoothly connected with the outerperipheral portion 14 through a bent part 15, and the outer peripheralportion 14 is formed into a tapered shape which extends from the bentpart 15. The diameter of the outer peripheral portion 14 is increasedtoward the inner side in the axial direction of the pulley (the Idirection indicated by the arrow in FIG. 1), and connected with an endpart 27 of a peripheral wall 2 on the side of an ear 22. The whole ofthe inner peripheral portion 13 is formed as a recess part 16 whichprojects into a space surrounded by the outer peripheral portion 14. Therecess part 16 is structured so that a bearing, which is not shown, isfitted into the recess part to be accommodated therein. The peripheralwall 2 has poly-V grooves 21 and the ear 22. The end part 27 on the sidewhere the ear 22 is formed is integrally connected with the outerperipheral portion 14 of the base part 1.

In the sheet metal pulley A of the embodiment, when a poly-V belt iswound around the peripheral wall 2 and the pulley is operated, vibrationand oscillation of the peripheral wall 2, which are caused by theoperation, are sufficiently propagated to the outer peripheral portion14 so that vibration and oscillation effectively occur also in the outerperipheral portion 14. In this case, the fulcrums of the vibration andoscillation are scattered in the end part 27 of the peripheral wall 2 onthe side of the ear 22 and also in the bent part 15, and hence thebending fatigue due to the vibration and oscillation is not concentratedinto the part where the end part 27 of the peripheral wall 2 on the sideof the ear 22 intersects with the outer peripheral portion 14.Consequently, cracking in the intersection part is prevented for a longterm.

In order to effectively prevent the crack formation from occurring, thetaper angle θ of the outer peripheral portion 14 may be set to be in therange of 15° to 70° or preferably 25° to 50° with respect to ahorizontal axis perpendicularly intersecting with the axial direction ofthe pulley (the I direction indicated by the arrow in FIG. 1).

FIG. 2 shows a sheet metal pulley A of a second embodiment of thepresent invention. In the sheet metal pulley A, the base part 1 ispartitioned into the inner peripheral portion 13 and the outerperipheral portion 14, and the inner peripheral portion 13 is smoothlyconnected with the outer peripheral portion 14 through the bent part 15,the peripheral wall 2 has the poly-V grooves 21 and the ear 22, and theend part 27 of the peripheral wall on the side where the ear 22 isformed is integrally connected with the outer peripheral portion 14 ofthe base part 1. These are the same as those of the first embodimentdescribed with reference to FIG. 1.

The embodiment is different from the first embodiment in that the innerperipheral portion 13 of the base part 1 has a center projection 17, andin that a flat annular part 18 surrounding the projection. The annularpart 18 is connected with the outer peripheral portion 14 through thebent part 15.

Also in the sheet metal pulley A of the second embodiment, when a poly-Vbelt is wound around the peripheral wall 2 and the pulley is operated,vibration and oscillation of the peripheral wall 2, which are caused bythe operation, are sufficiently propagated to the outer peripheralportion 14 so that the fulcrums of the vibration and oscillation arescattered also in the bent part 15. Therefore, the situation in whichone position, i.e., the intersection part of the end part 27 of theperipheral wall 2 on the side of the ear 22 and the outer peripheralportion 14 of the base part 1 is excessively fatigued and a crackformed, is prevented from occurring.

In the embodiments described above, the sheet metal pulley A has the ear22 of the single layer structure. It is a matter of course that thepresent invention can be applied also to the sheet metal pulley A suchas shown in FIG. 4 and having the ear of the double layer structure. Inthe embodiment shown in FIG. 1, the apex of the bent part 15 is slightlyhigher in level than the end part of the ear 22. It is a matter ofcourse that, in order to prevent the bent part 15 from projectingoutward in the axial direction, the level of the end part of the ear 22may be set so as to coincide with that of the apex of the bent part 15or the level of the apex of the bent part 15 may be set so as to beslightly lower than that of the end part of the ear 22. Furthermore, thelower face of the bottom wall of the recess part 16 of the innerperipheral portion 13 may be made to coincide with the level of thelower end part of the peripheral wall 2 to the extent that the recesspart does not protrude from the lower end part of the peripheral wall 2toward the outer side in the axial direction.

The sheet metal pulley of the present invention has a structure in whichthe connecting portion between the base part and the peripheral wall,and the ear hardly crack. Therefore, the present invention attains theeffect that the endurance life of the pulley can be prolonged ascompared with a prior art pulley.

The present invention may be applied to a pulley of the type in which aflat belt is to be wound around the peripheral wall, and also to that ofthe type in which the peripheral wall has a single V-groove so that aV-belt is to be wound around the peripheral wall.

What is claimed is:
 1. A sheet metal pulley, comprising: a base partwhich defines an axial direction; and a cylindrical peripheral wallintegrally formed therewith, said cylindrical peripheral wall having aninner side, an end part and an annular ear projecting outward from saidend part, whereinsaid base part includes an inner peripheral portion, abent part and an outer peripheral portion, said inner peripheral portionbeing connected with said outer peripheral portion by said bent part,wherein said outer peripheral portion is formed into a tapered shapewhich extends from said bent part, and wherein the diameter of saidouter peripheral portion is increased toward said inner side in saidaxial direction, with said outer peripheral portion being connected tosaid end part of said cylindrical peripheral wall on the side thereoffrom which said annular ear projects.
 2. A sheet metal pulley accordingto claim 1, wherein said outer peripheral portion forms a taper anglewhich is in the range of 15° to 70° with respect to a horizontal axisperpendicularly intersecting said axial direction.
 3. A sheet metalpulley according to claim 1, wherein said outer peripheral portion formsa taper angle which is in the range of 25° to 50° with respect to ahorizontal axis perpendicularly intersecting said axial direction.
 4. Asheet metal pulley according to claim 1, wherein said inner peripheralportion defines a recess part into which a bearing is to be fitted.